Enhanced metabolism & reduced effect w/ barbiturates, carbamazepine, phenytoin, primidone or rifampicin. Increased plasma conc w/ OCs or ritonavir. Excessive K loss w/ K-depleting diuretics eg, thiazides or furosemide. Increased risk of hypokalemia w/ amphotericin B, xanthines or β
2-agonists. Increased incidence of GI bleeding & ulceration w/ NSAID. Altered response w/ anticoagulants. Increased requirements of antidiabetic & antihypertensives. May decrease serum conc of salicylates & effect of anticholinesterases.